CiaoTo change the background for the panel right click on an empty spot and choose "properties" from the popup menu. Then switch to background tab and select "Solid color" or "Background Image". The problem is that some objects still have the stripes after applying these changes. An idea (probably a bad one) would be to find the image file that contains the pattern and delete it (make a backup first). You might also try to find the setting in gconf-editor.